Safety and tolerability of combination therapy with ambrisentan and tadalafil for the treatment of pulmonary arterial hypertension in children: Real-world experience.

OBJECTIVE: To describe the safety and tolerability of treatment with ambrisentan and tadalafil in pediatric pulmonary hypertension (PH). STUDY DESIGN: This retrospective observational two-center study included subjects (≤18 years of age) with PH receiving combination therapy with ambrisentan and tadalafil. Before initiating this therapy, many patients were on other therapies for PH. At baseline, patients either received no therapy or monotherapy with a phosphodiesterase 5 inhibitor (PDE5i) or endothelin receptor antagonist (ERA) (Group A), switched from a different PDE5i and ERA (Group B), or were on prostanoid therapy with or without a PDE5i and/or ERA (Group C and D). Demographics, symptoms, and adverse effects were collected. Pre- and postvalues for exercise capacity, hemodynamics, and biomarkers were compared. RESULTS: There were 43 subjects (26 F, 17 M) ages 4-17.5 years (median 9.3) with World Symposium of PH group 1, 3, and 5. Significant improvements were seen in change scores at follow-up in the entire sample and Group A for 6-min walk distance: +37.0 (6.5-71.0) [p = 0.022], mean pulmonary artery pressure: -6.0 (-14.0 to -3.5) [p = .002], pulmonary vascular resistance: -1.7 (-6.2 to -1.0) [p = .003], NT-proBNP -32.9 (-148.9 to -6.7) [p = .025]. WHO functional class improved in 39.5% and was unchanged in 53.5%; PH risk scores improved in 16%; were unchanged in 56%; and declined in 14%. Three patients discontinued therapy (two headaches, one peripheral edema). Seven patients were hospitalized for worsening disease (2/7 had a Potts shunt placed, 2/7 had an atrial septostomy). There were no deaths or lung transplantation. CONCLUSIONS: Combination therapy with ambrisentan and tadalafil was well-tolerated, with an acceptable safety profile in a select group of children. This therapy was associated with improved exercise capacity and hemodynamics in children who were treatment naïve or on monotherapy with a PH medication before the initiation of ambrisentan and tadalafil. Based on these early data, further study of combination therapy in pediatric PH is warranted.

Biomarkers of oxidative stress, inflammation, and vascular dysfunction in inherited cystathionine ß-synthase deficient homocystinuria and the impact of taurine treatment in a phase 1/2 human clinical trial.

STUDY OBJECTIVE: A phase 1/2 clinical trial was performed in individuals with cystathionine ß synthase (CBS) deficient homocystinuria with aims to: (a) assess pharmacokinetics and safety of taurine therapy, (b) evaluate oxidative stress, inflammation, and vascular function in CBS deficiency, and (c) evaluate the impact of short-term taurine treatment. METHODS: Individuals with pyridoxine-nonresponsive CBS deficiency with homocysteine >50 µM, without inflammatory disorder or on antioxidant therapy were enrolled. Biomarkers of oxidative stress and inflammation, endothelial function (brachial artery flow-mediated dilation [FMD]), and disease-related metabolites obtained at baseline were compared to normal values. While maintaining current treatment, patients were treated with 75 mg/kg taurine twice daily, and treatment response assessed after 4 hours and 4 days. RESULTS: Fourteen patients (8-35 years; 8 males, 6 females) were enrolled with baseline homocysteine levels 161 ± 67 µM. The study found high-dose taurine to be safe when excluding preexisting hypertriglyceridemia. Taurine pharmacokinetics showed a rapid peak level returning to near normal levels at 12 hours, but had slow accumulation and elevated predosing levels after 4 days of treatment. Only a single parameter of oxidative stress, 2,3-dinor-8-isoprostaglandin-F2α, was elevated at baseline, with no elevated inflammatory parameters, and no change in FMD values overall. Taurine had no effect on any of these parameters. However, the effect of taurine was strongly related to pretreatment FMD values; and taurine significantly improved FMD in the subset of individuals with pretreatment FMD values <10% and in individuals with homocysteine levels >125 µM, pertinent to endothelial function. CONCLUSION: Taurine improves endothelial function in CBS-deficient homocystinuria in patients with preexisting reduced function.

Human skin mast cells express complement factors C3 and C5.

We examine whether complement factor C3 or C5 is synthesized by human skin-derived mast cells and whether their synthesis is regulated by cytokines. C3 and C5 mRNAs were assessed by RT-PCR, and proteins by flow cytometry, confocal microscopy, Western blotting, and ELISA. C3 and C5 mRNAs were each expressed, and baseline protein levels/10(6) cultured mast cells were 0.9 and 0.8 ng, respectively, and located in the cytoplasm outside of secretory granules. C3 accumulated in mast cell culture medium over time and by 3 d reached a concentration of 9.4 ± 8.0 ng/ml, whereas C5 levels were not detectable (<0.15 ng/ml). Three-day incubations of mast cells with IL-1α, IL-1ß, IL-17, IFN-γ, IL-6, or anti-FcεRI did not affect C3 protein levels in culture medium, whereas incubations with PMA, TNF-α, IL-13, or IL-4 enhanced levels of C3 1.7- to 3.3-fold. In contrast with C3, levels of C5 remained undetectable. Importantly, treatment with TNF-α together with either IL-4 or IL-13 synergistically enhanced C3 (but not C5) production in culture medium by 9.8- or 7.1-fold, respectively. This synergy was blocked by attenuating the TNF-α pathway with neutralizing anti-TNF-α Ab, soluble TNFR, or an inhibitor of NF-κB, or by attenuating the IL-4/13 pathway with Jak family or Erk antagonists. Inhibitors of PI3K, Jnk, and p38 MAPK did not affect this synergy. Thus, human mast cells can produce and secrete C3, whereas ß-tryptase can act on C3 to generate C3a and C3b, raising the likelihood that mast cells engage complement to modulate immunity and inflammation in vivo.